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A003305 Figure 8's with 2n edges on the square lattice.
(Formerly M1860)
0
2, 8, 40, 208, 1120, 6200, 35236, 204664, 1210392, 7266824, 44184288 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,1

COMMENTS

Rotations and reflections are distinct. 2n is the total number of edges in the figure. Each "figure 8" is two of the polygons counted by A002931 intersecting at a single point. Like A003304 but now the smaller loop need not be a simple square. - Sean A. Irvine, Mar 21 2017

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=4..14.

S. G. Whittington and J. P. Valleau, Figure eights on the square lattice: enumeration and Monte Carlo estimation, J. Phys. A 3 (1970), 21-27.

CROSSREFS

Cf. A002931, A003304.

Sequence in context: A027617 A187071 A154626 * A076625 A139415 A119817

Adjacent sequences:  A003302 A003303 A003304 * A003306 A003307 A003308

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

a(11)-a(14) from Sean A. Irvine, Mar 21 2017

STATUS

approved

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Last modified December 13 00:17 EST 2017. Contains 295954 sequences.